Atomistic insights into Cu segregation effects on irradiation-induced defect dynamics in medium-entropy alloys

TL;DR

This study uses simulations to reveal how Cu segregation in medium-entropy alloys influences defect dynamics under irradiation, showing that Cu-rich regions trap defects, reduce dislocation density, and enhance irradiation resistance.

Contribution

It provides atomic-scale insights into how Cu segregation affects defect evolution and irradiation resistance in medium-entropy alloys, using hybrid MD/MC simulations.

Findings

Cu-rich domains trap defects and accelerate recombination

CSS shows reduced dislocation density and better irradiation resistance

Cu segregation influences defect nucleation and evolution

Abstract

Copper (Cu) segregation in medium and high-entropy alloys (M/HEAs) has shown significant influence on alloy properties. In this study, we investigate the effect of Cu segregation on evolution of irradiation-induced defects in FeNiCu, a model MEA, using hybrid molecular dynamics (MD) and Monte Carlo (MC) simulations. Thermodynamically driven hybrid MC/MD annealing at low temperature resulted in a partially decomposed Cu-segregated structure (CSS) and was compared with a random solid solution (RSS) and pure Ni. Results through cumulative displacement cascades reveal that Cu-rich domains in CSS act as defect traps, accelerating interstitial-vacancy recombination and suppressing defect cluster growth. The complex potential energy landscape (PEL) in CSS disrupts dislocation propagation, leading to spatially dispersed networks. Notably, CSS exhibits reduced stair-rod dislocation density compared to RSS, highlighting its superior resistance to irradiation swelling. Localized shear strain causes dislocations to preferentially nucleate in/near Cu-rich regions though their growth is hindered by chemical heterogeneity of the alloy. Notably, prolonged irradiation induces slow Cu segregation in the RSS structure, while slowly annihilating pre-existing Cu clusters in CSS simultaneously. The findings provide atomic-scale insights into the interplay between Cu segregation and irradiation-induced defect evolution in MEAs.